Various surgical procedures utilize devices to fixate anatomical tissue for healing. An example of a fixation device is an interference bone fixation screw, commonly referred to throughout the present description as "bone screw", used to fixate ligaments within bone tunnels during cruciate ligament reconstruction of the knee.
A surgical screw driver is commonly used to insert bone screws. This form of screwdriver has a rotatable drive shaft for rotating the screw, and advancing it along the longitudinal axis of the driver. The driver cooperatively engages with a drive recess, within the bone screw, to help achieve axial alignment of the screw with the drive shaft of the screw driver.
In cruciate ligament reconstruction, the bone screw is inserted into tandem isometrically positioned bone tunnels formed in the tibia and femur. A prosthetic ligament graft affixed to bone blocks at each end is inserted into the bone tunnel such that the ligament extends across the knee joint in the anatomical position of the cruciate ligament. The bone blocks are fixated within the bone tunnel by bone screws. Each bone screws is inserted in the bone tunnel so as to be disposed laterally between the walls of the bone tunnel and the bone block. Successful cruciate ligament reconstruction depends on the proper insertion of the bone screw along the longitudinal axis of the bone tunnel, parallel to both the tunnel walls and the bone block. Incorrect insertion of the bone screw causes screw divergence, resulting in increased difficulty in advancing the screw in the bone tunnel and reduced contact between the threads on the screw and the bone block. In addition, screw convergence can result in crushing or fracturing of the ligament and dislocation of the bone block, causing deviation of the ligament from an accurate, pre-established isometric position.
Cruciate ligament reconstruction is commonly performed as an open surgical procedure. Incisions on the order of 10 inches in length are utilized to access the knee joint. These relatively long incisions are required to provide room for the surgical screw driver to approach the tibial and femoral bone tunnels from directions aligned with the longitudinal axes of the bone tunnels and thereby to permit the driver to drive the bone screws effectively in a direction parallel with the bone block and the walls of the bone tunnels.
Open surgery possesses numerous disadvantageous compared to closed surgery or less invasive (arthroscopic) surgery for ligament reconstruction. These disadvantages include possible violation of mechanoreceptors in the knee, dessication of articular cartilage of the joint, increased tissue trauma resulting from incisions accompanied by increased patient discomfort and delayed post surgical mobility. In addition, hospitalization and rehabilitation times may be prolonged.
Accordingly, it is desirable to develop methods for performing cruciate ligament reconstruction that are less invasive, such as arthroscopic surgical procedures. Narrow portals are made with a puncture or stab wound in tissue adjacent to the knee of sufficient size to permit insertion of surgical instruments at the knee joint with the knee being visualized with an arthroscope. An arthroscope is here defined as any instrument for insertion into the cavity of a joint in order to inspect its contents. An example of an arthroscope is a fiberscope, which uses fiber optics to transmit images from the interior of the joint.
A method of arthroscopic cruciate ligament reconstruction can provide many benefits over open surgery, including reduced tissue trauma, decreased patient discomfort, earlier and aggressive range of motion and weight bearing without loss of fixation, reduced rehabilitation time and elimination of hospitalization because the procedures can be performed on an out-patient basis.
The limitations on maneuverability imposed by arthroscopic cruciate ligament reconstruction and the location of the arthroscopic portals in tissue adjacent to the knee mean that conventional drivers with straight drive shafts, which are used for placing bone screws into bone tunnels through incisions during open surgery, are not suited for this procedure.
Indeed, the anteromedial and anterolateral portals are angularly offset from the longitudinal axis of the femoral bone tunnel and therefore the direction of approach from such portals to the femoral bone tunnel to insert a bone screw is angularly offset also. The femoral bone tunnel opens on the femoral condyle at a site near the attachment site of the cruciate ligament. Longitudinal alignment of the screw driver with the opening of the femoral bone tunnel on the femoral condyle is difficult using conventional surgical drivers when the approach is made through the arthroscopic portals. This in turn presents difficulties in driving the screw parallel with the longitudinal axis of the femoral bone tunnel and the bone block in the tunnel.
Attempting to force the driver into parallelism with the longitudinal axis of the femoral bone tunnel runs a number of serious risks, including the possible breakage of the shaft of the driver at the knee: disengagement of the bone screws from the driver during manipulation and their contact with adjacent knee structures, followed by loss of the bone screw in the knee; and misalignment of the bone screw between the wall of the femoral bone tunnel and the bone block.
One compromise approach to the problem of location of arthroscopic portals is to introduce additional portals specifically for the purpose of inserting bone screws into the bone tunnel. One approach is to insert the bone screw through openings of the femoral bone tunnels on the lateral femoral cortex via portals placed proximally and laterally on the patients' thigh. This approach precludes the use of blind or closed end femoral bone tunnels. Alternatively, bone screws can be inserted through openings in the femoral condyle after their introduction through the tibial bone tunnels. In this case, the knee is hyperflexed to longitudinally align the tibial bone tunnel with the femoral bone tunnel, and hyperflexion must be maintained until the ligament is fixated in the femoral bone tunnel.
Angled drivers have been used in industrial applications as wrenches and screw drivers, and exemplary of such devices are U.S. Pat. Nos. 4,643,052 to Badiali, 4,620,458 to Schmidek, 3,788,169 to Nakayama, 3,696,694 to Boro, 3,232,151 to Blachowski, 2,042,376 to Balga, 1,428,282 to Glabaznya, 1,398,116 to Root, 2,199,823 to Sadtler, 933,639 to Frink and 877,571 to Larson. In medical applications, angled drivers have been used in power tools such as drills, and U.S. Pat. Nos. 5,041,119 to Frigg et al and 4,947,942 to Lightle et al are illustrative of angled, surgical power drills.
Prior art angled surgical drivers are unsuitable for use in least invasive, or endoscopic, surgical procedures to insert bone screws in bone tunnels directly from portals not aligned parallel with longitudinal axes of the bone tunnels. Moreover, angled surgical drivers in the prior art cannot effectively hold screws captive for insertion into the body through endoscopic size portals.